So I've made a second attempt at doing a SoundLab (ordered two PCBs a couple years back), and once again I am enjoying the silence as I hook it up. This time around I noticed that the batteries became to hot to touch, so I checked the resistance between + and - and it's something like 25 kOhm, which I guess is too little. So, a short somewhere I am guessing.

The first question is: will this have broken some component on the board?
Second: any other experience with short circuits in a SoundLab? Is there some position on the board that is more prone than others for shorts?
Third: should I take up knitting instead? (I actually saw this low resistance between + and - early on while doing the VCOs, since I've painstakingly measured the contacts of every component directly after soldering it. My procrastinating brain told me I could deal with this later - the logic of a moron).

The man that hath no music in himself, nor is not mov'd with concord of sweet sounds, is fit for treasons, stratagems and spoils; the motions of his spirit are dull as night and his affections dark as Erebus: Let no such man be trusted. - W. Shakespeare

Anyway, I fixed the envelopes - misread 500 Ohms as 500 kOhms (duh!). It's sonic mayhem here! The LFO is doing stuff it probably shouldn't do, but I like it so I'm going to leave it as it is. Only thing left fixing is the noise generator, but I rarely use those anyway...

Attaching some pics of my patented crows nest soldering technique, the finished item (built into my mother's cookie can) and a sample. Can you tell I'm happy I finally managed to pull off (sort of) an electronics project?

Great Job, Stefan!
Looks good in that cookie box - and I'm glad you were able to solve the problem.
Knitting is overrated - you might as well build more stuff.
You mentioned the 'silence' on the attempt a couple years back...did you ever get that one working?

The silence (and most of all really hot batteries) was solved by desoldering all the wires from the lid on the board, and the resoldering them more slowly component by component. So I started with the wires for the batteries and the VCO1. When I had those on, I hooked the scope to the output from VCO1, turned the thing on and looked at the wwaveform, which looked like an ok sawtooth with a little spike at the top.

Then I did the VCO2, and checked that in the scope, then the filter, EG, Noise, LFO and the rest. All the time feeling the batteries to see if they were going hot, which they never did. After a bit of headscratching and some small fix I had the thing making sound.

I still a bit confused about the EG. Ray says in his specific troubleshooting tips that I should se 8 or 9 volts at pin 1 of C2 and the ground, but I only see like 1 volt. At first I thought that was why the envelopes were so slow, but I traced that to the resistor mentioned earlier - it's still a low voltage there, but it works just like I would think it should: a clear envelope ramp wherever I try it out (VCAm VCO etc), with reasonable values for time and amplitude.

A similar confusion is there when I troubleshoot the noise generator. It says I should see a positive voltage on the emitter of Q7, but it's negative.

The LFO is behaving a bit strangely, but I don't think I want to troubleshoot that one, since the sounds are pretty cool.

The LFO is doing stuff it probably shouldn't do, but I like it so I'm going to leave it as it is.

how is it behaving?

note that the attenuation of the LFO and envelope is a little special so you will not get the expected result when connecting them to the oscillators. This is due to that they attenuate towards -9V instead of ground. I've modified those to choose either.

When I tweak the LFO amplitude, the pitch of the oscillators slides upwards and starts to sound like it's modulated by something. Turning the LFO frequency mostly does nothing, sometimes (when I am having a complex sound so it's difficult to hear exactly what's happening) I hear a very weak change up or down in pitch somewhere.

I think I'm going to open it up again and see if I can find what this is - esp. since the CV in for oscillator 2 doesn't work.

Tried out some CV from ChucK, and now the noise generator has decided to come alive all by itself! Instead, the resonance in the filter has decided to close down Well, well. Anyway, if anyone's wondering what a simplistic marriage between ChucK and a slightly broken MFOS SoundLab looks/sounds like, here it is. I love this!

Just reporting that I now have the thing working perfectly! One switch was slightly defect, meaning that it was always 'on' even though I flipped the switch. I noticed that pushing the wires changed the sound, and traced the source by push fewer and fewer wires until I noticed that it was the wire connected to that switch that changed the sound when I pushed it, or rather the pin on the switch needed to be pushed a bit to open the circuit. I solved it by pushing some elastic plastic in between the pins. This resolved the problem with oscillator 1 always being modulated by the LFO.

My final worry was that the LFO frequency knob didn't seem to change the frequency much - just a little. I traced this to the R94 resistor, where I had done the exact same error as with R6 and put in 500 kOhm instead of 500 Ohm. I only had a 470 Own resistor in my cache, and put that in, and now I have a working, nice sounding SoundLab in the can.

Now, what project should I take up next... I'm starting to get hooked on this - it's actually possible to do stuff and make it work!

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